The present invention is directed to electrical circuits selectively controlled to produce continuous and intermittent outputs, and, more particularly, the present invention is directed to such electrical circuits used to effect continuous or intermittent energization of the magnetron employed to supply microwave energy to a microwave oven or the like.
In a microwave oven food may be cooked by microwave energy generated by a magnetron or the like in a short time relative to the time normally required to cook the same food in a conventional gas or electric cooking appliance. A microwave oven also may be employed to defrost frozen food, but it has been found desirable when defrosting frozen food to operate the microwave oven intermittently or cyclically so as to avoid cooking the outer layers of the food load before the core thereof has fully thawed. Such intermittent or cyclical energization of a magnetron in a microwave oven is shown in U.S. Pat. Nos. 3,842,233, 3,824,365, and 3,694,608. During such cyclical energization of the magnetron the average power level of the microwave energy generated thereby is reduced, and in the off period during each complete cycle the temperature of the food load in the microwave oven will, to an extent, equilibrate, thus helping to avoid excessive temperatures at the surface of the food load while speeding the thawing process at the core. The same cyclical energization of the magnetron may also be advantageously used to cook certain foods at a relatively slower rate.